Box or furnace for electric heating apparatus



. No Model.)

0. L. OOFFIN. BOX OR FURNACE FOR ELEGTRIG HEATING APPARATUS.

No. 530,019. Patented Nov. 2'7, 1894."

I VEJVTOQ J, riff/Il ill/r 14 M/ESSES gwm M6. QMJMW rrno STATES CHARLES L. COFFIN, OF DETROIT, MICHIGAN.

BOX OR FURNACE FOR ELECTRIC HEATENG APFARATUS.

SPECIFICATION forming part of Letters Patent No. 530,019, dated November 27, 1894.

Application filed March 9. 1893. Serial No. 465,323- (No model.)

To all whom it may concern.-

Be it known that 1, CHARLES L. COFFIN, of Detroit, in the county of \Vayne and State of Michigan, have invented a new and useful improvement in a Box or Furnace for an Electric Heating Apparatus, of which the following is a specification.

My invention consists in an improved box or furnace for an electric heating apparatus,

hereinafter fully described and claimed, reference being made to the accompanying drawings, in -\vhich Figure 1 is a perspective view of a carbonholder connected with the furnace or furnacebox, the latter being in section. Fig. 2 is an enlarged sectional perspective view of the furnace, one end being omitted; Fig. 3 is a section through one partof the furnace-box, looking downward; and Fig. 4 is a top plan View of the furnace-box with the inner plate removed, and showing a slight modification in construction.

In heating metals by the action of a voltaic arc, in a furnace, the intense heat tends to disintegrate the furnace, andIhave found by considerable use thatafurnace of considerable life can be made as follows:

Referring to Figs. 1 and 2 s 5 represent soap-stone slabs or slabs of slate, lava, or any suitable material, which is for ordinary purposes considered a refractory non-conductor of electricity, forming insulating slabs, which form the sides and ends, and top or bottom of the furnace, the bottom slab being omitted in Figs. 1 and 2.

It will be noticed that the insulated slabs s, 8, shown in Fig. 2, project somewhat below the other parts of the furnace so that when the bottom slab is put in position and is secured by bolts engaging with threaded sockets, it will not come in contact with any of the interior linings.

0 represents the slabs of carbon, or mixtures of carbon with clay, or may be such mixtures as are known as carbon, brick, or graphite brickbut which for the purposes ofthis invention fulfill all the requirements of a slab of pure carbon, two of which are secured to the insulating sides .9 by a screw-bolt d, taking into a threaded socket b. The inner slab c is recessed as shown, to receive the head of bolt d and protect it from the fire.

The aperture it through the insulating sides 3 is continued through the carbon slabs 0, but made larger through said carbons for the purpose of preventing contact between the carbons between which the voltaic arc is formed and said slabs c, the hole h being made of such size through the insulating side 8 to be somewhat snugly closed by the arc carbons.

1 represents a refractory block such as lime or magnesia or graphite cut to fit between the inner carbon slabs c c and provided with shoulders to engage with the recess in said carbon slabs and thus protect the heads of bolts 01.

WVhile the insulating slabs may be threaded to receive the bolts which fasten the sides and top or bottom of the furnace together firmly, I prefer to screw into said insulated slabs a thimble a which is screw-threaded on its outside to engage with the bolt, whereby repeated operations of the bolt or screw do not tend to wear off the threads on the insu= lated slab.

As shown in Fig. 3, three sides of the furnace indicated by 7, may be made of iron, the other side f being also made of iron and connected with the remainder of the box by screw-bolts e which pass through insulation 01, which is also interposed between the sides f andf', as clearly shown in the figure. If this iron box be used, instead of the insulating slabs, it is advisable for the purpose of preventing short circuiting that the carbon slabs c, with which the side f is lined, shall not be in electrical contact with any other of thecaroon slabs c lining the other part of said box, as clearly shown in said drawing.

In Fig. 4 the insulating sides sare retained for three sides and the fourth is made direct by two carbon slabs c, the outer one of which may be recessed to form an air space between them, as shown in the drawings, and in this construction care should be taken that said. carbon 0 forming one side of the furnace must not come in electrical contact with any of the carbon slabs lining any other side of the furnace. In Fig. 4 the outer side containing the air space is secured in position by bolts e engaging threaded sockets b.

By keeping all of the carbon slabs c on the different sides of the furnace out of electrical contact with each other, a short circuit between the are forming carbons is prevented, as this would interfere with the maintenance of the vol taic arc in its proper location. I have found by repeated trials that a furnace lined in this way with a refractory top, such as lime or magnesia, or graphite, and double carbon slabs at; the sides will last under continued use for a long time, the only thing which requires renewal being the inner carbon slabs, and by the construction shown these slabs can be usually renewed at the end of thirty or sixty days, or whenever too much eaten away by simply unscrewing the bolts e and bolts d,and putting a new carbon in place.

The furnace or furnace box, constructed as described, may be used in connection with the carbon-holder exhibited by Fig. 1, where the letters E E represent two carbon holders, whose upper ends form nuts e, 6 one of which is tapped with a right hand screwthread. while the other is tapped with a lefthand screw-thread, to engage with screwthreads on shaft W, said screw-threads being of different pitch, and both nuts e, e are bored to fitand slide on guide-rods g, g. W represents a shaft journaled in said head h, h and lugs J J lying between guide-rods g g, and provided at one end with a hand'wheel G. The ends of shafts W outside of lugs J J are right and left-hand screw-threaded, the pitch of one of said screw-threads being about double that of the other, so that when by rotation of said shaft the nuts e, e are moved,

the motion of one of said nuts will be faster than the motion of the other, so that one of the carbon-holders E E carried on said nuts 9 a will advance faster than the other to compensate for the greater rapidity of combustion of the positive carbon.

The carbon-holders E E are adapted to hold carbons which project into the furnace or furnace-box through the passages h, the construction being such that the arc can be regulated.

i/Vhat I claim as my invention, and desire to secure by Letters Patent, is-

1. A furnace for electrically heating metals, consisting of a box composed of separable parts secured together by bolts, having its sides and ends lined with double slabs of carbon, the lining of the sides and ends being insulated from each other, and having its top or bottom, as the case may be, lined with a refractory slab,such as lime, magnesia or graphite, substantially as shown and described.

2. A furnace for electrically heating or welding metal, consisting of a box formed of the refractory insulating slabs 8 provided with threaded sockets a, secured together by bolts 6 and lined with the carbon slabs c secured in position by the bolts d and threaded sockets b, and the lime or magnesia top or bottom, substantially as shown and described.

CHARLES L. OOFFIN.

Witnesses:

GERTRUDE H. ANDERSON, GEO. I-I. LOTHROP. 

